Optical loss is a limiting factor in the design and construction of optical networks and links, which typically include hundreds of kilometers of silica-based optical fiber. Consequently, a reduction in the loss of the fiber by even hundredths of decibels per kilometer would have a significant impact on the performance of such networks. Optical losses in silica fibers are predominantly caused by two factors, including (1) Rayleigh scattering, which falls off as a function of 1/λ4 and which dominates for shorter wavelengths, and (2) infrared absorption by the silica, which dominates for longer wavelengths. As is well known in the art, the product of these two forms of optical loss falls to a minimum at a wavelength of approximately 1560 nm. Consequently, most optical signals are transmitted at a bandwidth centered around 1560 nm in order to minimize transmission losses. At a bandwidth between 1510-1610 nm losses typically vary between a minimum of 0.189 dB/km and a maximum of 0.200 dB/km. As small as this may seem, such a loss rate still translates into a 50 percent loss of signal over a distance of 15 km, which is quite significant when one considers that some networks (such as the one traversing the Atlantic Ocean) are over 6,500 km long.
While there have been various attempts in the past to develop an optical fiber with lower transmissivity losses, the high costs associated with the manufacture of such fibers has prevented them from enjoying widespread use. So called silica core fibers, e.g., those having an undoped silica core and a fluorine doped cladding, are known which have reduced losses on the order of 0.151 db/km at 1550 nm are known. However, it is well known that silica core fibers are much more difficult to manufacture than fibers having cores which include index of refraction-altering dopants. Other types of fibers with potential for low loss are known which employ a non-silica chemistry. However, the materials used in such fibers are far more expensive than silica, and cannot be drawn and worked on a commercial scale without the development of completely different kinds of manufacturing equipment than is presently in use.